Constant CEILING_12 

const CEILING_12: &str = "If a Request ID equal to or larger than this is received by the endpoint \
                          that sent the MAX_REQUEST_ID in any request message (ANNOUNCE, FETCH, \
                          SUBSCRIBE, SUBSCRIBE_ANNOUNCES or TRACK_STATUS_REQUEST), the endpoint \
                          MUST close the session with an error of 'Too Many Requests'.";